1. Field of the Invention
The present invention relates to rail bogies for hooking with semi-trailers and the like road vehicles to form trains for riding on rails. It is of the type disclosed in my prior Canadian application No. 561,449 filed on Mar. 15, 1988.
2. Description of the prior art
In the said application, there is disclosed a twin-axle rail bogie over the wheeled truck of which is mounted, through an air spring suspension, a lift assembly supporting a platform having a pair of fifth-wheels for connection of the bogie with king pins of a pair semi-trailers so that the latter and the bogie together form part of a railway train. The platform lift assembly is wholly mechanical, being constituted by a plurality of combinations of coupled worms and worm-wheels of which the worm-wheels drive screws moving up and down to raise and lower the fifth-wheel platform.
In such an arrangement, the loads coming from the semi-trailers are constantly supported by the pneumatic suspension but only through this mechanical lift assembly. Consequently, the latter is permanently subjected to heavy stresses generated when the bogie is jolted. It follows that the lift assembly is prone to deteriorate rapidly because of its mechanical nature.
Known to the present Applicant are the following U.S. Pat. Nos., not pertinent to the present invention:
4,416,571 PA0 4,547,107 PA0 4,669,391 PA0 4,685,399 PA0 4,773,335 PA0 4,766,818
Thus U.S. Pat. Nos. 4,416,571 and 4,685,399 relate to rail bogies having a pair of fifth-wheels for connection with semi-trailers but mounted directly on the chassis of the bogie. In U.S. Pat. No. 4,547,107 each of the fifth-wheels each of the two fifth-wheels is individually lifted by means of a power jack. In such respects, these patents are not pertinent to the present invention. The remaining patents are even less pertinent, as will be seen from the description that follows.